Attorney-General John Rau said he was not convinced mandatory sentencing was the best way to deal with the problem and examples of its use in the Northern Territory had not been encouraging.

"I think in the Northern Territory, for example, they had 'three strikes and you're in' laws and a lad who pinched a packet of chewies wound up going to jail because it's his third offence, so you get bizarre outcomes with mandatory sentencing," he said.

Mr Brokenshire said police had tried for years without success to negotiate with the Government for mandatory sentences.

"I call upon the Government to either support the Family First bill or table their own," he said.

The Law Society said there was no evidence that mandatory sentences made communities safer and ample penalties already existed for such crime.

It feared mandatory penalties would undermine the independence of courts.